Diamond-like carbon coated golf club head

ABSTRACT

A diamond-like carbon (DLC) coated golf club head primarily for reduction of friction between the hitting surface and the golf ball at impact. The DLC coating comes in two varieties including dehydrogenated DLC or hydrogenated DLC and is thinly applied between about 0.1 and 10 μm. The diamond particle size of individual diamond-like carbon molecules or crystals can be less than 0.1 μm, and preferably less than 1 nanometer. The DLC coating may be bonded to the golf club head or hitting surface using cathodic arc method or other applicable methods at temperatures of less than 200° C.

[0001] The present application is a continuation-in-part applicationbased on a U.S. patent application filed on Apr. 7, 1999, and having theSer. No. 09/287,241.

FIELD OF THE INVENTION

[0002] The present invention relates generally to improvements in theperformance of a golf club, especially golf clubs used for distance.More specifically, the invention relates to the coating of the face orhitting surface of a golf club head with diamond-like carbon (DLC) todrastically reduce the frictional coefficient on the face of the golfclub head, thereby increasing golf ball distance and accuracy.

BACKGROUND OF THE INVENTION

[0003] Golf is a very popular sport among people of all ages. As such,the golf equipment industry is constantly seeking to improve the designof golf equipment, especially golf clubs, to meet the demands of manygolfers trying to improve their game or obtain a competitive edge overfellow golfers. There have been numerous attempts over the years toimprove the performance of golf clubs and indeed, this continues today.

[0004] Essentially, the game of golf can be broken down into two majorskills, the long game and the short game. The long game involves skillssuch as “driving” a golf ball long distances from the tee box and/orhitting a golf ball long distances from the fairway. The short gameinvolves skills such as “pitching” a golf ball from a location near theputting green and “putting” the golf ball from a spot on the green intoa hole. Since the skills utilized in the long game and the short gameare different, club designs vary accordingly, i.e., a putter is designeddifferently than a driver.

[0005] When considering how one might improve the performance of a golfclub, there are essentially two major variables that should beconsidered. First, the properties of the shaft may be considered whenseeking to increase performance of a golf club. For example, golf clubshafts have traditionally been designed using metal materials. However,there has been a recent trend toward the use of graphite shafts.Additionally, the shaft length and/or the angle relationship between theshaft and the golf club head may be modified to alter performance. Theselatter two alterations are typically made when a person wishes to havetheir clubs customized.

[0006] Second, and more applicable to the present invention, the designof the golf club head itself effects the performance of a given club.Particularly when using clubs such as drivers and other long game clubs,the distance and direction that a golf ball travels is critical. As aresult, many different geometric shapes and materials have been tried inorder to vary the design of golf club heads in hope of achieving highperformance, i.e., increased distance and improved accuracy.

[0007] Regarding geometric shape of golf club heads, many differentshapes have been manufactured. For example, there has been a recenttrend toward the design of driver heads with increased volume.Additionally, clubs commonly called “irons” have evolved from havingsolid golf club heads to golf club heads having perimeter weighting.Perimeter weighted golf club heads have many advantages over older clubsincluding increased distance and increased control of a golf shot.

[0008] Regarding the material used to construct golf club heads, manymaterials have been used including hard wood (e.g., persimmon), metal(e.g., steel, cast iron, aluminum, copper, titanium), graphite (e.g.,Thunder Head wood from Spalding®), plastic (e.g., Odyssey as describedin U.S. Pat. No. 5,342,812 issued to G. Rennie) or other materials(e.g., metal matrix composite as described in U.S. Pat. No. 8,342,812issued to P. Niskanen et. al.). Presently, drivers are primarily madefrom titanium or iron.

[0009] An important part of a golf club is the face of the club head.The face of the club head can best be described as the hitting spot orsurface. This is where the golf club interfaces with the golf ballduring a golf swing. When a golf ball is struck, the material at thecontact point or hitting surface will deform elastically and thenrebound immediately. Though this cannot be entirely prevented, reductionof this deformation is desirable so that the energy of the swing can bemore effectively transferred to the golf ball. As a result, manyattempts have been made to improve the rigidity of the material used ingolf club heads. This is particularly true with regard to the face orhitting surface of the golf club head.

[0010] When considering materials with high rigidity, one candidate toconsider is diamond. In U.S. Pat. Nos. 4,951,953 and 5,029,865 issuingto D. Kim, a ball striking surface of a golf club head is disclosedhaving diamond coating for increased surface rigidity. The particles canbe embedded using an electroless “composite diamond coating” technique.Specifically, the patent claims the use of a composite comprising adiamond component and a metal or metal alloy such as a nickel matrix.The entire thickness of the composite coating can be from 1 to 2 mils.Alternatively, in U.S. Pat. No. 5,620,382 issuing to H. Sam Cho, et al.,the use of a polycrystalline diamond or cubic boron nitride insert isdisclosed. The insert is comprised of a surface layer (bondeddiamond-diamond or CBN-CBN crystals) and a hard or rigid support layer.The insert is then inserted, i.e., cemented in a metal or ceramicmatrix, into a cavity on the golf club head.

[0011] Though diamond has the highest modulus of rigidity, there aresome basic problems with the use of diamond or diamond powder ingeneral. First, because the hitting surface is so hard, there is verylittle deformation of the club head creating a greater impact force. Asa result, the golf ball, which is much softer than the club, experiencesmore ovalation than is typically experienced. Thus, the contact areabetween the hitting surface of the club head and the golf ball isincreased momentarily. Because the contact area is increased, thefrictional force between the hitting surface of the club head and thegolf ball is also increased. In other words, because there is morecontact between the golf ball and the hitting surface, there is morefriction. Moreover, there are additional problems when a diamond-metalcomposite is used in that diamond is much harder than metal. Therefore,when a diamond-metal composite is polished, diamond grains, being morerigid than metal, will not wear down at the same rate as metal therebycausing the diamond grains or particles to protrude higher than themetal matrix after polishing. This unevenness will further increase thefrictional force between the hitting surface of the club head and thegolf ball.

[0012] Higher frictional force between the hitting surface and the golfball is generally undesirable because unless the golf ball is perfectlyhit, there is a greater likelihood of “hooking” or “slicing” a givenshot. “Hook” and “slice” are golf terms used to describe the direction agolf ball travels when the path of flight is not linear, but arcuate ina direction toward or away from the golfer respectively. This occurs asthe golf ball spins on a more vertical axis. Therefore, the higher thespin rate, the more curvature, i.e., “hook” or “slice”, the flying ballwill experience. These type of shots are normally undesirable for tworeasons. First, the distance that the golf ball travels is reducedbecause energy is wasted on angular momentum, i.e., spin, and heatgenerated from the increased friction. Both of these energies reduce thedesired forward momentum. Second, since the desired direction iscompromised, the next shot becomes more difficult. Additionally, thoughback spin is desirable for some shots, even back spin will diminish thedistance of a golf shot.

[0013] With regard to diamond hitting surfaces of club heads, there arealso economic concerns. The preparation of diamond-metal composite (PCD)requires somewhat difficult and expensive modifications of a golf club.First, in order to insert a composite into a club head, the hittingsurface must be machined to create a cavity or void for insertion of thediamond-metal composite. Additionally, diamond-metal composite isexpensive and the process of preparation is tedious making this optionunaffordable to most golfers. Moreover, the hitting surface of a clubhead containing a diamond-metal composite requires frequent polishingand/or grinding. This additional work is time consuming and difficult toaccomplish due to the presence of diamond.

[0014] In addition to issues surrounding rigidity, attempts have alsobeen made to reduce the friction on golf club heads. For example, U.S.Pat. No. 5,885,171 issuing to Sharpe on Mar. 23, 1999 discloses a systemfor altering the friction coefficient between a golf club face and agolf ball. This patent teaches that a liquid coating, such as alubricant, can be applied to the face or hitting surface of a golf clubto lower the frictional coefficient. Though the goal of lowering thefrictional coefficient is worthy, there are several disadvantages to thesystem disclosed in U.S. Pat. No. 5,885,171. First, applying a liquidlubricant is messy and if the golfer is not careful, the lubricant canget on the golfer's hands causing slippage on subsequent swings. Second,some lubricant will surely pass from the golf club head to the ballcausing the ball to fly through the air unevenly. Third, many golf shotsnecessarily require that the golf club strike the substrate or earthprior to hitting the golf ball. As such, some lubricant will be wipedfrom the club prior to striking the ball. Finally, it is inconvenient tobe required to apply a liquid lubricant to a golf club prior to a golfshot, and further, be required to remove the same lubricant from thegolf club head when completing a golf round.

[0015] A second example of a patent that discusses the reduction offriction on a golf club head can be found in U.S. Pat. No. 5,531,444issuing to Buettner on Jul. 2, 1996. In that patent, a coating oftitanium nitride as applied to a golf club head is disclosed. The patentstates that the coating of titanium nitride provides a “very hard,tough, and low-friction coating.” However, to coat a metal golf clubhead with titanium nitride, high temperatures must be used. The patentfurther states that precautions must be taken to prevent the golf clubhead from deforming or distorting, i.e., “the bore in the club headhozzle tends to distort.” As such, the patent claims a method to preventdistortion of the club head hozzle. Though the inventor has succeeded atpreventing distortion of the “club head nozzle,” the development of asuperior coating is desirable that has a lower friction coefficient anddoes not require high temperatures to apply, thereby preventingdistortion and/or weakening the golf club head.

[0016] It has been recognized that it would be desirable to provide agolf club head that is relatively inexpensive to manufacture, isreasonably rigid at the hitting surface, does not distort when a coatingis applied, and drastically reduces the frictional force between thehitting surface and the golf ball on impact.

SUMMARY OF THE PRESENT INVENTION

[0017] The present invention pertains primarily to an improved golfclub, more particularly, an improved golf club head. The golf club headof the present invention is comprised of a body having a hitting surfaceand a coating of diamond-like carbon (DILC). The diamond-like carbon(DLC) is used to coat a golf club head, particularly the hitting surfacebut including the lower surface, at a thickness of between about 0.1 and10 μm. Additionally, the diamond-like carbon (DLC) of the coating canhave a grain size or diamond molecule size of less than 0.1 μm. Largerdiamond grain sizes can increase the friction between the golf club headhitting surface and the ball to less desirable levels compared to thoseof the present invention. Preferably, the present invention is intendedto coat iron and/or titanium golf club heads, though golf club headsmade from different materials or composites can also be used.

[0018] Regarding the diamond-like carbon coating, there are essentiallytwo types that may be used in the present invention. First, diamond-likecarbon (DLC) containing less than 10% (by atoms) of hydrogen may be used(hereinafter “dehydrogenated DLC”). If dehydrogenated DLC is used, thepercentage of diamond in the diamond-like carbon (DLC) will be from 50%to 95% by atoms. A more preferred percentage range of diamond is from80% to 95% by atoms. Second, diamond-like carbon (DLC) containing atleast 10% by atoms of hydrogen may be used (hereinafter, “hydrogenatedDLC”). If hydrogenated DLC is used, the percentage of diamond in thediamond-like carbon will be from 20% to 60%. A more preferred percentagerange of diamond is from 30% to 60% by atoms.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In the accompanying drawings which illustrate embodiments of theinvention:

[0020]FIG. 1 is a perspective view of a golf club head indicating thepreferred locations for coating; and

[0021]FIG. 2 is a cross-sectional view of a golf club head coated invarious areas with a diamond-like carbon (DLC)

DETAILED DESCRIPTION OF THE INVENTION

[0022] Before the present invention is disclosed and described, it is tobe understood that this invention is not limited to the particularprocess steps and materials disclosed herein as such process steps andmaterials may vary to some degree. It is also to be understood that theterminology used herein is used for the purpose of describing particularembodiments only and is not intended to be limiting as the scope of thepresent invention will be limited only by the appended claims andequivalents thereof.

[0023] It must be noted that, as used in this specification and theappended claims, singular forms of “a,” “an,” and “the” include pluralreferents unless the content clearly dictates otherwise.

[0024] In the accompanying drawings, FIG. 1 shows a perspective view ofa golf club head 10 having a diamond-like carbon (DLC) coated hittingsurface 12. Additionally, a diamond-like carbon (DLC) coated lowersurface 14 is shown. Turning to FIG. 2, a cross-sectional view of thegolf club head 10 is shown. Both a diamond-like carbon (DLC) coatedhitting surface 12 and a diamond-like carbon (DLC) coated lower surface14 are shown as adhered to a body 16 of the golf club head 10.

[0025] With these figures in mind, the present invention is drawn to agolf club head comprising a body having a hitting surface wherein thehitting surface is coated with from 0.1 μm and 10 μm of diamond-likecarbon (DLC) coating, and wherein the diamond-like carbon (DLC) of thecoating has a grain size or molecule size of less than 0.1 μm. In oneembodiment, a lower surface is also coated with from 0.1 μm and 10 μm ofdiamond-like carbon (DLC) coating. There, the diamond-like carbon (DLC)of the coating can also have a grain size of less than 0.1 μm. Thus,practically speaking, when diamond is present, the lower end of theparticle size (with respect to both the hitting surface and the bottomcoating) can be as small as a single tetrahedral carbon moleculedimension. In one embodiment where the bottom surface is coated, thehitting surface coating and the bottom surface coating can be a singlecontinuous coating. In this embodiment, the rest of the golf club orgolf club head need not be coated likewise, though such coating is notprohibited. In another embodiment, the diamond-like carbon (DLC) coatingcan extend from the hitting surface to another part of the head.

[0026] Though the grain size or molecule size can be as large as lessthan 0.1 μm, it is preferred that the diamond-like carbon (DLC) of thecoating have a grain size of less than about 1 nanometer. In a morespecific embodiment, the diamond-like carbon (DLC) grain size can beamorphous, also known as distorted tetrahedral carbon.

[0027] With the present invention, the coating can be applied to a metalgolf club head. Though other composites can also be used, metal golfclub heads such as iron or titanium are preferred for this invention.Further, though the entire golf club head can be coated withdiamond-like carbon (DLC), the hitting surface must be coated withdiamond-like carbon (DLC) for the invention to have the desired effectwith respect-to the golf ball. However, it may be desirable to coatother surfaces, such as the bottom surface, to reduce friction as thegolf club head brushes the grass, dirt or other substrates.

[0028] Generally, diamond-like carbon (DLC) is essentially a compositeof diamond, graphite or non-diamond carbon, and/or a polymer. Morespecifically, diamond-like carbon (DLC) is a composite material that cancomprise three end members. First, diamond which is carbon boundtogether with sp³ bonds (tetrahedral) can be present. Second, graphitewhich is carbon bound together with sp² bonds (triagonal) can bepresent. Third, a polymer such as a hydrocarbon plastic can be presentas well. Thus, the carbon portion is substantially supplied by graphiteand/or diamond, and the hydrogen is substantially provided by thepolymer. In one embodiment, the diamond-like carbon (DLC) coating cancomprise diamond, graphite, and a hydrocarbon plastic. In an alternativeembodiment, the diamond-like carbon (DLC) coating can comprise diamondand a hydrocarbon plastic. In yet another embodiment, the diamond-likecarbon (DLC) coating comprises randomly assembled diamond carbon atomsand graphite carbon atoms, thus forming an amorphous coating structure.

[0029] For practical purposes, diamond-like carbon (DLC) can be dividedinto two major categories. The first category includes thosediamond-like carbons (DLC) that contain at least 10% hydrogen by atom,i.e., hydrogenated DLC having more polymer present. The second categoryare those diamond-like carbons (DLC) that contain less than about 10%hydrogen by atom, i.e., dehydrogenated DLC having less hydrogen present.The hydrogenated DLC contains from 20% to 60% diamond by atom whereasdehydrogenated DLC contains from 50% to 95% diamond by atom.

[0030] As stated, carbon may form either sp² bonds or sp³ bonds. sp²bonds indicate the presence of graphite and sp³ bonds indicate thepresence of diamond. The ratio of these two types of bonds may bemeasured by Raman spectroscopy which is well known in the art. This issignificant because the number of sp³ bonds (diamond) determines thecloseness of diamond-like carbon (DLC) to diamond. Thus, hydrogenatedDLC is less rigid or hard than dehydrogenated DLC. Though this is thecase, all diamond-like carbons (DLC) have a very low frictionalcoefficient. However, the frictional coefficient of hydrogenated DLCincreases in the presence of water or moisture. Conversely,dehydrogenated DLC is less affected by moisture. Therefore, wetconditions from rain or humidity will not adversely affect theperformance of golf club heads coated with dehydrogenated DLC. As aresult, dehydrogenated DLC is preferred for the present invention,although hydrogenated DLC can also be used.

[0031] To utilize the present invention, at least one layer ofdiamond-like carbon (DLC) can be coated on the face or hitting surfaceof the golf club head. As mentioned, other surfaces can also be coatedas needed, e.g., the lower or bottom surface of the golf club head maybe coated so that the club head brushes the substrate with reducedfriction whereas the upper or top surface need not be coated.Additionally, when applying a layer of diamond-like coating (DLC) to thegolf club head, the coating can be deposited directly on the desiredsurface, e.g., the hitting surface and/or the bottom surface. Therefore,it is not necessary to form a cavity or otherwise alter the shape ortexture of the golf club head as is required by some of the prior art.

[0032] The coating of metal substrates with diamond-like carbon (DLC) isnot a new concept. Specifically, industry has deposited diamond-likecarbon (DLC) onto various materials using primarily physical vapordeposition (PVD). This method energizes carbon atoms at low temperaturesby physical means. Physical vapor deposition (PVD) is contrasted tochemical vapor deposition (CVD) which energizes carbon atoms by heatingthem to a high temperature, i.e. above 600° C. Due to the hightemperatures required for CVD, PVD is the method of applyingdiamond-like carbon (DLC) that is preferred. Specifically, PVD methodsknown in the art include techniques such as sputtering, ion beamdeposition, and cathodic arc (though cathodic arc is a more preferreddeposition method for the present invention). However, the mentioning ofthese methods is not intended to limit the invention as other methodsused for coating golf club heads with diamond-like carbon (DLC) arepossible.

[0033] One reason that the use of diamond-like carbon (DLC) on thehitting surface of a golf club head is desirable, especially withrespect to long game golf clubs, is that diamond-like carbon (DLC) has avery low frictional coefficient, i.e., 0.1 or less. This low frictionalcoefficient is comparable to teflon or other lubricants. Low frictionbetween the hitting surface of a golf club head and the golf ballreduces heat and spin or angular momentum that a golf ball normallyexperiences after impact. Therefore, more forward or directionalmomentum is transferred from the golf club to the golf ball. In otherwords, the force behind a golf club swing is not wasted on angularmomentum or generated heat.

[0034] Another advantage of the present invention is that to obtain alow frictional coefficient, the user is not required the use of a liquidlubricant as discussed in U.S. Pat. No. 5,885,171. The use of a liquidlubricant can be messy and if the golfer is not careful, the lubricantcan get on the golfer's hands causing slippage on subsequent golfswings. Further, since the lubricant is not integrated into the golfclub head, some lubricant will pass from the golf club head to the ball.This will cause the ball to fly unevenly or asymmetrically. The presentinvention provides a golf club head having a low friction coefficient(0.1 or less) on the hitting surface without the disadvantagesassociated with the use of lubricants.

[0035] Still another advantage of the present invention is that thediamond-like carbon (DLC) can be deposited on the golf club head orhitting surface at a relatively low temperature, i.e., less than 200° C.This is significant because the properties of the base metal, i.e.,substance that the golf club head is made of, will not be overheatedcausing alterations to the dimension or properties of the golf clubhead. Therefore, applying the diamond-like carbon (DLC) to a titanium oriron golf club head will not adversely affect the shape, relativestrength or hardness of the golf club head. Further, the presentinvention addresses the issues presented in the previous discussion ofU.S. Pat. No. 5,531,444 by providing a coating (DLC) that can be appliedat a relatively low temperature. As such, the bore in the golf club headhozzle will not distort during the coating process. Additionally, sincediamond-like carbon (DLC) is a relatively smooth substance, polishing ofthe respective golf club heads is minimized if not eliminated where thediamond-like carbon (DLC) has been applied.

EXAMPLE

[0036] 50 titanium drivers were coated with dehydrogenated DLC using thecathodic arc method. The deposited amorphous or distorted tetrahedraldiamond was applied at a thickness of about 3 micrometers. The clubs,having diamond-like carbon (DLC) coated heads, were used by manygolfers. Most felt that their golf performance, in particular, theirdriving distance (due in part to lower degree of hook and slice) hadnoticeably improved when using diamond-like carbon (DLC) coated golfclub heads.

[0037] While the invention has been described with reference to certainpreferred embodiments, those skilled in the art will appreciate thatvarious modifications, changes, omissions and substitutions can be madewithout departing from the spirit of the invention. It is intended,therefore, that the invention be limited only by the scope of thefollowing claims.

What is claimed is:
 1. A golf club head comprising: a body having ahitting surface wherein said hitting surface is coated with from 0.1 μmand 10 μm of diamond-like carbon (DLC) coating, and wherein saiddiamond-like carbon (DLC) of said coating has a grain size less than 0.1μm.
 2. A golf club head as in claim 1 further comprising a lowersurface, said lower surface being coated with from 0.1 μm and 10 μm ofdiamond-like carbon (DLC) coating, and wherein said diamond-like carbon(DLC) of said coating has a grain size less than 0.1 μm.
 3. A golf clubhead as in claim 1 wherein said diamond-like carbon (DLC) comprisesdistorted tetrahedral carbon.
 4. A golf club head as in claim 1 whereinsaid diamond-like carbon (DLC) of said coating has a grain size lessthan 1.0 nanometer.
 5. A golf club head as in claim 1 as in claim 2wherein the hitting surface coating and the bottom surface coating is asingle continuous coating, and is not present elsewhere on the golf clubhead.
 6. A golf club head as in claim 1 wherein the diamond-like carbon(DLC) coating extends from the hitting surface to another part of thehead.
 7. A golf club head as in claim 1 wherein the hitting surface hasa frictional coefficient of less than 0.1.
 8. A golf club head as inclaim 1 wherein said golf club head is comprised primarily of materialselected from the group consisting of iron and titanium.
 9. A golf clubhead as in claim 1 wherein said diamond-like carbon (DLC) contains lessthan 10% (by atoms) hydrogen.
 10. A golf club head as in claim 9 whereinsaid coating of said diamond-like carbon (DLC) is from 50% to 95% (byatoms) diamond.
 11. A golf club head as in claim 10 wherein said coatingcontaining said diamond-like carbon (DLC) is from 80% to 95% (by atoms)diamond.
 12. A golf club head as in claim 1 wherein said coatingcontaining said diamond-like carbon (DLC) contains at least 10% (byatoms) hydrogen.
 13. A golf club head as in claim 12 wherein saidcoating containing said diamond-like carbon (DLC) is from 20% to 60% (byatoms) diamond.
 14. A golf club head as in claim 13 wherein said coatingcontaining said diamond-like carbon (DLC) is from 30% to 60% (by atoms)diamond.
 15. A golf club head as in claim 1 wherein said diamond-likecarbon (DLC) is deposited to said hitting surface by physical vapordeposition method (PVD).
 16. A golf club head as in claim 15 whereinsaid physical vapor deposition method (PVD) is cathodic arc method. 17.A golf club head as in claim 12 wherein said diamond-like carbon (DLC)is deposited to said hitting surface at a temperature less than 200° C.18. A golf club head as in claim 1 wherein the diamond-like carbon (DLC)comprises diamond, graphite, and a hydrocarbon plastic.
 19. A golf clubhead as in claim 1 wherein the diamond-like carbon (DLC) comprisesdiamond and a hydrocarbon plastic.
 20. A golf club head as in claim 1wherein the diamond carbon atoms and the graphite carbon of thediamond-like carbon (DLC) coating are randomly assembled, forming anamorphous coating structure.